For illumination, lighting devices have been widely used. Generally, a lighting device includes a lamp holder, a lighting bulb installed on the lamp holder, and a lampshade disposed around the lamp holder for converging lights from the lighting bulb. Consumers may purchase the lamp holder, the lighting bulb and the lampshade in one set, or as individuals. In case of the latter, an additional support post is needed to assemble together the lamp holder and the lampshade that are purchased from different suppliers. It may be difficult to obtain a support post that is matchable with both the lamp holder and the lampshade.